The invention relates to a method for operating a battery arrangement of a motor vehicle, in particular a fraction battery of the motor vehicle.
Moreover, the present invention relates to an apparatus for operating a battery arrangement of a motor vehicle, in particular a traction battery of the motor vehicle, wherein the apparatus can be electrically coupled to a heating/cooling arrangement for heating or cooling the battery arrangement.
An electric cell or rather a battery is an electrochemical energy storage device and an energy converter. In the case of charging the battery, stored chemical energy is converted into electrical energy by means of an electrochemical reaction. The electrical energy can be used by a consumer that is electrically coupled to the battery. In principle, a differentiation is made in the case of batteries between primary batteries and secondary batteries. Primary batteries can only be charged once and not recharged. In contrast, secondary batteries can be recharged. The term ‘battery’ is used hereinunder as a synonym for the secondary battery or rather the secondary cell.
A battery is used in motor vehicles for the purpose inter alia of providing electric current for the headlamps, the on-board electronics and for the starter for starting the combustion engine. In the case of electric or hybrid vehicles, the battery is also used as an energy storage device for the electric drive of motor vehicles. Said battery consequently has a significant role in determining the performance and range of the vehicle. For this reason, it is essential that the state of the battery in the case of electrically driven vehicles is constantly monitored in order for the driver to be aware of the useable energy store.
A battery management system (BMS) is used for the purpose of monitoring and controlling the re-chargeable battery and said battery management system is used in an additional interface between the vehicle and the electronic components that are installed in the battery. The battery management system assumes various functions, such as for example cell protection, charge monitoring, load management, determining a charge state and thermal management for the purpose of setting an optimal operating temperature.
Traction batteries (for example lithium ion battery) that are usually used in electrically driven vehicles have in general the characteristic that they function efficiently only within a limited temperature range. Below this temperature range, the current losses greatly increase and the maximum output is no longer available. If the battery is operated outside the temperature range, this can lead to an accelerated aging of the battery and even to the battery becoming damaged. In the case of known methods, the temperature of the battery is therefore set in such a manner that during the operation of the motor vehicle the battery is always operating within the limited temperature range. Methods are also known whereby the temperature of the battery is only held within the optimal temperature range if the motor vehicle is connected to an external energy source. In this case, the energy consumption that results from heating or cooling of the battery has a negative effect on the range of the motor vehicle. Furthermore, it is possible in the case of a motor vehicle that is shut down (also without an external energy supply) to check regularly whether an upper temperature threshold of the temperature range is exceeded. If this is the case, the battery is accordingly cooled for the purpose of protecting components. In the case of very low temperatures, the battery is usually not checked regularly and possibly overheats. In fact, the battery is heated to a higher temperature as required, for example during a planned journey. However, the described procedures of cooling or respectively heating the battery require a high output of energy. In the case of an electrically driven vehicle during the driving operation or respectively in the case of a motor vehicle that is shut down without being connected to an external energy supply, the achievable range of an electrically driven vehicle is consequently considerably reduced. Even if the motor vehicle is connected to an external energy supply, the cooling and heating procedures result in an overall increased current consumption by the electric vehicle and as a result poor energy efficiency.